Water-dispersible sulfopolyesters incorporating polyethylene glycol (PEG) units are known in the art. For example, U.S. Pat. Nos. 3,546,008, 3,734,874 and 3,779,993, teach compositions useful as a size for fabrics. These references disclose a very large number of linear compositions that are limited to PEG contents of greater than 15 mol %, based on 100 mol % of total glycol, within a PEG molecular weight range of 106 to 898 g/mol. Although it is disclosed that more than one PEG could be present in a particular composition, there is no teaching or example of the advantageous use of combinations of polyethylene glycols having different molecular weights.
The incorporation of high molecular weight PEGs is the subject of U.S. Pat. No. 4,233,196, where a molecular weight range of 106 to 22,018 g/mol was specified for the PEG component. Although both low and high molecular weight PEGs could be incorporated in a particular composition, the invention was limited to less than 15 mol % of total PEG based on 100 mol % of total glycol.
U.S. Pat. Nos. 4,329,391, 4,483,976, 4,525,524, and 5,290,631 disclose additional water-dispersible sulfopolyester compositions. However, all of these patents are limited to PEGs having molecular weights of less than 600 g/mol.
Recently, European Patent Application 0 761 795 described hot melt adhesives based on 10-90 weight percent of a sulfonated polyester, which can be the condensation product of a difunctional dicarboxylic acid, a sulfomonomer containing at least one metallic sulfonate group, a glycol, and optional ingredients. There is no disclosure of using both high and low molecular weight PEGs.
The utility of certain water-dispersible sulfopolyester compositions as adhesive raw materials is also described in detail by the teachings of U.S. Pat. Nos. 5,543,488; 5,552,495; 5,552,511; 5,571,876; and 5,605,764, and European Patent Application EP 0 761 795 A2.
Among the many problems associated with prior art compositions utilizing sulfonated polyesters is the distinctive and unpleasant odor associated with the final product. The odor is highly undesirable, particularly when used, for instance, as an adhesive composition. It would be beneficial if a composition could be formulated having the advantageous aspects of sulfonated polyesters without the undesirable odor.
The prior art disclosures relating to water-dispersible sulfopolyesters do not recognize the advantageous combinations of both low and high molecular weight PEGs and the benefits thereof. In addition, none of the examples given above are described as block copolyesters, indicating that the inventors were unaware of the structure/property advantages obtainable from specific architectures.
However, it is important to recognize that a block architecture, by itself, will not necessarily lead to desired property improvements. In some cases a block architecture may actually have a deleterious effect on properties; for example, a high content of certain high molecular weight PEGs in the final polymer may lend unacceptable water-sensitivity to a particular article of manufacture. Therefore, it is not obvious which block compositions will render the key property improvements that are described hereinafter.
Thus there is a need for a water-dispersible sulfopolyester composition that has improved properties, particularly a low odor, that can be made by simple selection of the proper block architecture.